Problem: 5 folders cost $7.75. Which equation would help determine the cost of 3 folders?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. If we let $x$ represent the cost of 3 folders, we have the following proportion: $\dfrac{x}{3}$ We have to pay $7.75 for 5 folders, and that can be written as a proportion: $\dfrac{\$7.75}{5}$ Since the price per folder stays the same, these two proportions are equivalent. $\dfrac{x}{3} = \dfrac{\$7.75}{5}$